Refrigerating apparatus and method



Oct. 25,1938. 1.. B. M. BUCHANAN REERIGEZRATING APPARATUS AND METHOD F'IGQI.

FICLZA Filed Oct. 28, 1936 INVENTOR Lssu: BM. bucHnunN as sea IO I5 20 FICLE.

ATTORN Y Patented Oct. 25, 1938 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS AND METHOD of Pennsylvania Application October 28, 1936, Serial No. 107,935

10 Claims.

My invention relates to refrigeration and has foran object to provide an improved method and apparatus for controlling the operation of a refrigerating element.

A further object of my invention is to provide an improved method and apparatus for controlling the eifective cooling area of an evaporator structure.

A still further object of the invention is to provide an improved two temperature refrigerator which is inexpensive to produce.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

Fig. 1 is a diagrammatic view of a two temperature refrigerator embodying my improved ap- 'paratus;

Fig. 2 is a diagrammatic sectional view of a detail employed in the apparatus shown in Fig. 1; and

Fig. 3 is a diagram showing the pressure-tem-' perature characteristics of .two volatile fluids which may be employed in my improved apparatus. Reference will now be had to the drawing wherein I have shown my invention applied to apparatus including a cabinet structure l0 having relatively low and high temperature cooling chambers ii and i2 formed therein and cooled by respective evaporator elements l3 and i4. The evaporator l3 receives refrigerant in preference to the evaporator l4 and the two may be connected in series, as shown, for the flow of refrigerant.

A refrigerant condensing unit l5 circulates refrigerant through the evaporators l3 and I4 and includes a compressor l6 driven by a motor i1, and a condenser l8, the latter being cooled in any suitable manner such as, for example, by a motor driven fan i9. Vaporous refrigerant is with- "drawn from the evaporator M by the compressor it through a conduit 2i and is compressed to a relatively high pressure in the condenser I! wherein it is cooled and condensed; The con-- densed refrigerant isdelivered to areservoir 22 that is connected to the evaporator i3 by a conduit 23. An expansion device 24 is disposed in the conduit 23 for reducing the pressure of the refrigerant whereby it may be vaporized at relatively low temperature.

The foregoing apparatus operates on the wellknown compressor-condenser-expander refrigerating cycle. When the chamber II is toibe cooled, vaporization of refrigerant is effected in the evaporator i3 only and the vapor passes through a connection 25 to the evaporator l4 and thence through conduit 2| to the compressor I6. At this time, the device 24 controls the admissionof condensed refrigerant so that only gaseous refrigerant is discharged to the evaporator I4.

Refrigeration of the chamber I2 is effected by evaporating'refrigerant in the evaporator H, at which time the evaporator I3. is filled with liquid 10 refrigerant. The device 24 admits refrigerant in quantities sufficient to effect overflow of condensed refrigerant into the evaporator l4 through the connection 25. Refrigerant may be vaporized in both evaporators I3 and I4 at this time, but it is principally vaporized in the evaporator i4 due to the higher temperature thereof.

The means for effecting the foregoing opera-, tion will now be described. Reference will be had to the device 24 that is shown enlarged in section in Fig. 2. While other forms of expansion devices may be employed in accordance with my invention, I prefer to construct the device 24 similar to a conventional thermostatic expansion valve, but operating differently therefrom. The device 24 includes a casing 26 having chambers 21 and 28 formed therein, which communicate. respectively, with the liquid conduit 23 and the evaporator L3. A valve 29 controls communication between the chambers 21 and 28 and is actuated by a diaphragm 3| that is subjected to the pressure of the refrigerant in the chamber 23 and evaporator l3.

The casing 26 preferably defines a chamber 32 above the diaphragm 3| that communicates with a container or bulb 33 by means of a conduit 34, The bulb 33 contains a volatile fluid and is secured in heat exchange relation with the connec I tion 25. The pressure of the volatile fluid in the bulb 33, conduit 34 and chamber 32 is a function of the temperature'of the refrigerant within the connecting conduit 25 and, is impressed on the upper side of the diaphragm 3|. Accordingly, the pressure corresponding to the saturated temperature of the refrigerant in the evaporator i3 biases the valve 29 in closing direction and the pressure in the chamber 32, which varies with the temperature of the refrigerant discharged through the connecting conduit25, biases the valve 29 in valve opening direction. An adjustable spring 30, biasing the valve in. valve opening direction, may

- beemployed for adjusting purposes to be referred -to hereinafter. I have discloseddzhe. device 24 diagrammatically for the. sake of cleamess and it will be understood that, in practice, refinements is g . not necessary for the purpose of illustration would be employed.- For example, the device 24 would be so constructed that transfer of heat between the chambers 28 and 32 is minimized.

In accordance with my invention, I employ fluid in the bulb 33 which has diiferent temperature pressure characteristics than the characteristics of the refrigerant employed, in that the pressure of the fluid varies less with a given change in temperature than the pressure of the refrigerant. As an example, sulphur dioxide (S0 may be provided in the bulb 33 when dichlorodifluoromethane (CChFz) is employed as the refrigerant in the system. The curves shown in Fig. 3 disclose, approximately, the pressure-temperature characteristics of these fluids.

A valve of the character described in the foregoing controls the superheat inthe vapor discharged from the evaporator l3 in such manner that the superheat is relatively high when the pressure and saturated temperature of the refrigerant is high and progressively decreases the amount of superheat in the vapor as the pressure and saturated temperature is reduced.

Accordingly, the evaporator It contains a relatively small amount of liquid when thetemperature of vaporization is high, which liquid is vapor izedand superheated before passing through the conduit 25 to the evaporator it. When the temperature of vaporization in'the evaporator I3 is depressed to a predetermined value, the superheat is'reduced to zero and the evaporator i3 is fllled with liquid refrigerant which passes through the conduit 25 to the evaporator. l4 wherein it is vaporized. t

The foregoing operation may be made clear by considering pressures gand temperatures of the fluids above and below the diaphragm 3| under twodiiferent temperatures of vaporization in the evaporator It. "It will be assumed that the superheat is zero when the temperature of the refrigerant (CClzFr) is --5 F., so that liquid refrigerant passes through the conduit 25 to the evaporator Id. The pressure of the refrigerant -'tofore.

impressed on the under side of the diaphragm 3| is approximately 21% lbs. per sq. in. absolute as shown at A i.in Fig. 3. As the temperature of the fluid (80:) in the chamber 32 is also 5' F., the pressure thereof is approxmiately 9 lbs. .per sq. in. absolute as shown in Fig. 3 at 3". This represents a pressure differential of 12% lbs. per

' sq. in. on the diaphragm which is opposed by the bias of the spring 30. Under these pressure values, the valve 29 is actuated to admit liquid refrigerant in such quantities that the evaporator- I! is filled and overflow into the evaporator ll When the temperature of vaporization in the evaporator is 15 F.,Ithe absolute pressure of the refrigerant in the evaporator 13 and the chamber 28 is approximately 32% lbs. per in. absolute as shown at C in Fig. 3. 'As; thebias of the v spring Ill represents 12 /2 lbs. per sq. in., the pressure of the fluid above the diaphragm equals the diiference or 20 lbs. per sq. in. absolute. Sulphur dioxide, at 20 lbs. per sq. in.'absolute, corresponds to a temperature of approximately 27 F. as shown at D" in Fig. 3, or the temperature of the vapor passing through the conduit 25. Accordingly, the vapor is superheated 12 F. when vapor- 'izedat15F. L

,amount of superheat in the vapor leaving the 7 evaporator I; will be progressively decreased as I 5 From the foregoing, it will be apparent that the the'saturated temperature decreases from'15 F.

to -5 F. and that the amount of liquid refrigerant in the evaporator I 3 will progressively increase until it overflows into the evaporator H at 5 F. The temperature at which superheating of the refrigerant ceases may be varied by adjusting the bias of the spring 30. Suitable means may be provided for adjusting the spring 30, such as for example, a screw 35, projecting exteriorly of the casing 26. Increasing and decreasing the bias of the spring 30 respectively increases and decreases the saturated temperature within the evaporator 13 at which superheating'ceases.

Automatic control of the operation of the con- .den'sing unit IS in response to temperature conditions within the chambers II and i2 may be provided. As shown, a thermostat 36 of the gas type and responsive to the temperature of the evaporator l3, may be employed for actuating a switch 31 that controls energization of the compressor motor H. The source of power for the motor I! is'represented by line conductors L1 and La. A thermostat, shown by way of example of the 'expansible metal type and responsive to the temperature of the air in the chamber .12,

may also control operation of the condensing unit IS. The thermostat 38 may be connected in parallel with the thermostat 36, as shown. Operation As shown in the drawing, both thermostats as and 38 are in their circuit open position as the v temperature of evaporator l3 and the air within the chamber l2 arebeldw values at which the respective thermostats close and energize the motor I]. Assume a rise in the temperature of the evaporator I: to a value of 15 F., for extemperature the thermostat It acts to open the.

switch 31 whereby the condensing unit It stops and circulation of refrigerant ceases. During the refrigeration of the evaporator II, the superheat 1n the vapor is gradually reduced and the effective cooling area of the evaporator l3 gradually increases. The superheat in the vapor at -3 1". is of relatively low value so that only superheated vapor is passed to the evaporator it during refrigeration of the evaporator ii. In this connection, it will be assumed that superheating of the vapor in the evaporator I 3 ceases at 5' F.

- When the temperature of the air in the chamber l2 increases to a predetermined value, the "thermostat 38 effects operation of the condensing unit ii for the circulation of refrigerant.

Cooling'of. the evaporator i3 is first effected until its temperature is depressed to -5 F. or

the temperature at which liquid refrigerant is passed to the evaporator l4. vaporization is effected in the evaporator l4 for cooling air in the chamber l2 and continues until the temperature thereof is depressed to the desired value at which time the thermostat 28 opens and terminates operation of the condensing unit l5.

From the-foregoing, it will be apparent that cooling of the evaporator l3 preceeds cooling of the evaporator ll when the latter requires cooling as vaporization can only be effected in the I evaporator l4 when the temperature of the evaporator I3 is depressed to 5 F. in the example under consideration.

I heating of the vapor in the evaporator 13 ceases and liquid refrigerant passes to the evaporator It. This operation continues until the thermostat 38 is satisfied and operates to terminate operation of the condensing unit IS.

The form of control system described is shown by way of example and it will beunderstood that other forms may be employed to control a refrigerating system constructed in accordance with my invention, v

From the foregoing, it will be apparent that I have provided an improved method and apparatus for controlling the operation of a refrigerating element wherein the effective cooling area thereof progressively increases as the temperature and pressure of vaporization therein decreases. It will be apparent, furthermore, that I have provided a novel two temperature refrigerator which is simple in construction and which may be inexpensively produced.

It is tobe understoodthat the specific forms of the refrigerator cabinet structure and of the condensing unit disclosed are shown by way of exampleand that other suitable forms of these elements may be employed equally well without departing from the spirit of my invention.

While I have shown the device 24 for controlling the vaporization of refrigerant and the effective area of the evaporator structure as a thermostatic expansion valve, it will beunderstood that my invention contemplates the employment of other suitable'devices for this purpose.

While I have shown my invention in but one form, it will be obvious to those skilled inthe art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

l. The method of controlling the operation of first and second refrigerant evaporators which comprises, admitting condensed refrigerant to the evaporators in such manner that it fiows into the first evaporator in preference to the second evaporator, conveying vaporized or condensed refrigerant from the first evaporator to the second evaporator, and controlling the superheat in the refrigerant conveyed from the first to the second evaporator in such manner that. the superheat progressively decreases as the pressure of the refrigerant progressively decreases, whereby superheated refrigerant vapor is conveyed to the second evaporator when the pressure of the refrigerant is relatively high and liquid refrigerant is conveyed to the second evaporator when the pressure is relatively low.

2. In refrigerating apparatus, the combination of relatively low and l'il'gh temperature evaporators, means for supplying refrigerant to the evaporators, and first and second temperature responsive means for controlling the operation of the refrigerant supply means, said first temperature responsive means being effective to operate the refrigerant. supply means so that vaporization is effected in the low-temperature evaporatorand said second temperature responsive means being effective to operate the refrigerant supply means so that vaporization is effected first in the low temperature evaporator and thence in the higher temperature evaporator.

3. In refrigerating apparatus, the combination of first and second evaporators, means for supplying condensed refrigerant to the evaporators so that the condensed refrigerant flows into the first evaporator in'preference to the second evaporator, and means for controlling the fiow of condensed refrigerant to the evaporators in response to the superheat of the refrigerant vaporized in the first evaporator, said means effecting a relatively high superheat when the pressure of the vaporized refrigerant isrelatively high and progressively decreasing the amount of superheat in the vaporized refrigerant as its pressure decreases, whereby the amount of liquid. refrigerant in the first evaporator increases as its pressure decreases until liquid refrigerant substantially fills the first evaporator and overfiows into the second evaporator when the pressure is reduced to a predetermined value.

4. Inrefrigerating apparatus, the combination of first and secondevaporator elements, means for condensing refrigerant vaporized in the evaporator elements, means for conveying the condensed refrigerant to said evaporator elements in such manner that the condensed refrigerant flows into the second element only after the first element is filled with condensed refrigerant, and means responsive to thesuperheat of the re-., frigerant vaporized in the first evaporator element for controlling the admission of condensed refrigerant to the evaporator'elements, said controlling means effectinghigh superheat when the temperature of the vaporized refrigerant is relatively high and, zero superheat when the tem perature of the vaporized-refrigerant has been reduced to a predetermined low value, at which time condensed refrigerant is passed to the sec- 0nd evaporator element.

5. In refrigerating apparatus, the combination of first and second evaporators, means for supplying condensed refrigerant to the evaporators first evaporator until filled and thence into the a second evaporator, means responsive to the evaporator for controlling the flow of condensed so that the condensed'refrigerant fiows into therefrigerant to the evaporators, said means effecting a progressive reduction in said temperature difierence as the pressure and saturated'ternperature of the refrigerant is decreased, whereby v the first evaporator is partly filled with liquid refrigerant when its temperature isrelatively high and is substantially filled with liquid refrigerant when itsv temperature is depressed to a predetermined value, at which time liquid refrigerant is delivered to the second evaporator for vaporization therein.

6. In' refrigerating apparatus, the combination of means defining low and higher temperature cooling chambers, first and second evaporators disposed for cooling the low and higher temperature chambers, respectively, said first and second evaporators being connected in series in the order named-for the flow of refrigerant therethrough,

circulating means for withdrawing vaporous refrigerant from the second evaporator and for translating condensed refrigerant to the first evaporator and a device for controlling the flow 5 of condenser refrigerant and responsive to the superheat of the refrigerant vaporized in the first evaporator, said device being so constructed and arranged that the superheat in the vapor is progressively reduced as the pressure of the refrigerant is reduced, whereby the portion of the first evaporator which contains liquid refrigerant progressively increases as the pressure of vaporization decreases; the arrangement being such that superheated vapor is admitted to the second evaporator'when the pressure and temperature of the refrigerant in the first evaporator is relatively high and liquid refrigerant is ad- 'mitted to the second evaporator for vaporization therein when the pressure of the refrigerant is relatively low.

7. The combination as claimed in claim 6 including first and second means responsive to respective temperatures in the low and higher temperature cooling chambers for controlling the g5 operation of the circulating means.

8. In a refrigerating system, the combination of a source of condensed refrigerant, an evaporator, a valve for controlling-the admission of the condensed refrigerant to the evaporator, a pressure responsive device actuated by the pressure of the refrigerant vaporizedin the evaporator for actuating the valve, and an element respon- =sive to the final temperature of the vaporized refrigerant and having a volatile fluid therein,

5 the pressure of which is a function of said final temperature, and which is impressed on the pressure responsive device in opposition to the pressure of the va rized refrigerant, said volatile :fluid having pr v ure-temperature characteristics which differ from the pressure temperature char- ,acteristics of the refrigerant controlled thereby in that the pressure of the volatile fluid varies less with a given change in temperature than the pressure of the refrigerant.

1 9. The method of operating a refrigerant evaporator having a passage in which liquid refrigerant is admitted to one end and is removed from a second end as a vapor or a liquid, which includes applying heat to the refrigerant as it passes through the passage, evaporating the liquid refrigerant at saturation temperature, raising the temperature of the vapor, controlling the admission of the liquid to the passage in accordance with the difference between the final superheat temperature and the saturation temperature, and progressively reducingsaid temperature difierence to zero as the saturation temperature is reduced to' a predetermined value, whereby the portion of the passage containing liquid moves progressively toward said second end until liquid is discharged therefrom.

10. The method of, controlling the operation of a refrigerant evaporator which comprises ad-' mitting condensed refrigerant to a portion of the evaporator for vaporization, withdrawing the vaporous refrigerantfrom a second portion of the evaporator, controlling the admission of condensed refrigerant to the evaporator in response to predetermined values of the superheat in the withdrawn vapor and progressively reducing said superheat values-in response to progressive reductions in the pressure and temperature of the vaporous refrigerant.

LESLIE 3. M BUCHANAN.

CERTIFICATE OF CORRECIEOIL Patent No. 2,1 ,950. October 5 958- LEsLIEfB. M. BUCHANAN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: P age2, first column, lirie 61, afterthe word. "per" insert sq.; and that the said'Letters Patent shouldbe read with this correction therein thgt the eenie conformjto the record of the case in the Patent Office. u V

Signed and sealed this 15th day of December, A. D. 1958.

" Henry Van aired-ale 1 (Seal) Acting Commissioner of Patents. 

